Audio distortion on MacBook Pro

Test with headphones or external speakers. If the issue is only with the built-in speakers, then the laptop will need to be repaired. Have Apple or an Apple Authorized Service Provider examine the laptop to provide you with a repair estimate.

FYI, it really helps to mention the exact model Mac you have since some laptops like the MBPro 2013-2015 models (especially the 2014 model) are known to have speaker failures. I've never seen any other Apple laptop models (or any other non-Apple laptops) have such a high rate of speaker failures. You can get the exact model of the Mac by clicking the Apple menu and selecting "About This Mac".